During operation, motor vehicles can become electrostatically charged. This can be due, for example, to mechanical friction between two components, for example, a rotating shaft in the transmission, or due to the friction of the tread surfaces of the pneumatic vehicle tires as they roll on the road. Normally, the electrostatic charge is dissipated to the road via the pneumatic vehicle tires. This is possible because the materials of which they are composed include electrically conductive materials, especially rubber compounds. If the electrostatic charge is not dissipated from the motor vehicle, the electronics of the motor vehicle may be compromised, for example. There are legal requirements for the electrical resistance of a motor vehicle. The total resistance, measured between the tread surface of the pneumatic vehicle tire and the rim, should not exceed 10+6Ω, that is, the pneumatic vehicle tire must be conductive.
It is furthermore known that the fundamental characteristics of the pneumatic vehicle tire, such as grip, rolling resistance and flexibility, can be improved by using materials with a high proportion of silicon dioxide, particularly in the rubber compound of the tread. The use of silicon dioxide (SiO2), which is also referred to as “silica” or “silicic acid”, stabilizes the network of bonds between the individual substances in a rubber compound. In comparison with the conventional structure comprising two nodes (sulfur and carbon), the three-node structure formed in this way (sulfur, carbon and silicate) increases the strength of the material. Furthermore, the use of silicon dioxide improves the adhesion of the pneumatic vehicle tire on the roadway since the rubber compound can be made softer owing to its higher strength.
However, the use of silicon dioxide has the disadvantage that the electrical conductivity of the pneumatic vehicle tire decreases. Since the electrostatic charges are dissipated from the motor vehicle essentially via the pneumatic vehicle tires, the use of silicon dioxide, which has lower or only slight conductivity, is therefore problematic. With an increasing proportion of silicon dioxide in the rubber compound of the tread, the pneumatic vehicle tire has a lower electrical conductivity or a higher electrical resistance than pneumatic vehicle tires with a higher proportion of carbon black in the tread.
A pneumatic vehicle tire having the characteristics described above comprises at least a tread with an outer electrically non-conductive tread cap with a profiled tread surface, an inner tread base and a non-conductive belt bandage as an intermediate ply of a woven type between the tread base and the belt arranged thereunder. The proportion of silicon dioxide in the pneumatic vehicle tire is increased, in particular, by means of the belt bandage including silicon dioxide, thereby improving the characteristics of the pneumatic vehicle tire. The tread base and the tread cap are also referred to by specialists in this area as the “base” and the “cap”.
To improve electrical conductivity, the formation of a plurality of electrically conductive conductivity strips, referred to as “carbon center beams” (CCB), on the base of the tread is already known. These conductivity strips extend in a radial direction from the base, through the outer tread cap, to the tread surface and thus form an electrical connection to the road surface. Another known practice is that of forming a multiplicity of gaps or openings in the electrically non-conductive belt bandage, the openings bridging the electrical connection between the pneumatic vehicle tire and the road surface.
DE 198 50 766 B4 discloses a pneumatic vehicle tire having a belt and a tread arranged between the belt and the tread surface. The tread is constructed from a radially outer and a radially inner rubber ply, wherein the radially inner rubber ply has two regions of different rubber compounds. In addition, a further region is formed, which extends from the belt to the tread surface and is composed of a conductive rubber compound containing a high proportion of carbon black. Here, the radially outer rubber ply corresponds to the non-conductive tread cap and the radially inner rubber ply corresponds to the conductive tread base. The further region forms an electrically conductive connection between the base and the tread surface of the pneumatic vehicle tire or the road surface.
Moreover, U.S. Pat. No. 5,942,069 discloses a pneumatic vehicle tire having a tread composed of an electrically non-conductive material or a material of poor conductivity that has a profiled tread surface and an inner electrically conductive tread base. The pneumatic vehicle tire described here is distinguished by at least one radially projecting, integrally formed extension of the tread base, which extends radially outward from the tread base to the tread surface.
U.S. Pat. No. 7,188,654 furthermore discloses a pneumatic vehicle tire containing a belt bandage comprising a ply that has strengthening members embedded in an unvulcanized rubber compound, wherein the strengthening members run substantially parallel to one another within the ply and are hybrid cords, which are constructed from a first twisted yarn with a high elastic modulus and a second twisted yarn with a low elastic modulus, which are twisted together at the ends.